Abstract
KEYWORDS
(noise, vehicle, acoustic comfort, insulating and absorbing materials.)
ABSTRACT
The tendency to improve man`s living and working conditions as well as the concern for human environment protection cause the improvement of the acoustic characteristics of the motor vehicles to become one of the producers main tasks. Cars have influence over passengers by means of great number of characteristics and functions, and the noise that is emitted from the car towards the passenger compartment has especially direct and intense influence. The noise inside the vehicle has a central character, so that it suppresses the effect of other characteristics and is lately considered as one of the vehicle performances. Besides, not every objectively silent noise inside the car is considered pleasant, measured in dB(A). In the mixture of noises, the silent noises can cover much louder ones while being in effect, so that they are the only one that can be perceived. Apart from the level of noise, the spectral structure and the distribution of amplitudes are of great importance. In general it means that one noise is in so much less burdensome if it is more silent. The aim of the research, as the part of this work , is testing the possibility of vehicles acoustic comfort improvement by using the cheaper insulating materials on the vehicles partition wall.
The possibility to reduce noise on the tract of its transmission will be discussed about in this work. In other words, the possibility of reduction enlarging of the already formed sound energy and reduction of its conduction into the passenger compartment will be analysed. By changing the insulating material and acoustic processing of the fire wall of the vehicle, the inner noise can be reduced, as well as its separate components, and by that acoustic comfort of the vehicle can be improved. According to this, the acoustic comfort representing the quality degree is defined, that is, the vehicle quality from thew point of view of acoustic comfort. The parameters of the vehicle acoustic comfort are defined here as: the level of noise, the frequency spectrum, loudness and the articulation index. The speech has its own spectrum that comprises all sounds. The noise in the car masks the speech or music so that it brings the driver and passengers into the awkward situation when they cannot understand each other while having communication. The awkwardness can be reduced by influencing on the sources, that is, by cutting the noise transmission track with the aim of reducing the global levels and frequency levels of speech area. The insulating and absorbing materials whose acoustic influence is significant in the frequency speech area has a specific place.